Substituents Effects on the Properties of Polyhedral Oligomeric Silsesquioxanes(POSS)/Poly(L-lactic acid) Hybrid Films

Abstract

In this paper, polyhedral oligomeric silsesquioxanes (POSS) with three different substituents are blended with poly(L-lactic acid) (PLLA) solution to prepare the hybrid films. The three types of POSS are octa(3-chloroammoniumpropyl)silsesquioxane (OCAPS), octa(3-chloropropyl)silsesquioxane (OCPS) and octavinylsilsesquioxane (OVPS). The effects of POSS substituents on the dispersion and properties of PLLA are investigated by means of SEM, XRD, DSC, DMA, POM, TGA, tensile and in vitro tests. The results show that OCAPS and OCPS have better dispersion states than OVPS, supported by the fact that an obvious phase separation is observed in OVPS/PLLA hybrid film. OCAPS and OVPS hybrid materials show higher T gs than that of PLLA, whereas OCPS acts as a plasticizer to decrease the T g of PLLA. Meanwhile, the T ms of PLLA are all decreased by the incorporation of the three POSS. The thermal stability of PLLA has been improved by the presence of OCPS and OVPS. The addition of POSS does not change the crystalline structure of PLLA and POSS appears as the heterogeneous nucleating agents in PLLA matrix, as the T cs of POSS/PLLA in the reheating cycles shift to lower temperatures. The elongations at break point of OCAPS and OCPS hybrid films increase due to their plasticizer effect when the mechanical force is put on. The hydrophobic character of OCPS and OVPS prohibits the degradation of PLLA, however, OCAPS/PLLA shows faster degradation rate than PLLA due to the high hydrophilic property of OCAPS.